Elongate members such as optical or electrical cable, pipelines, risers used in hydrocarbon extraction, etc., particularly but not exclusively those deployed underwater, are often positioned adjacent other structures such as other elongate members, buildings, rock formations, etc. There is often a need to provide physical separation between the elongate members and the other structures to protect the elongate member and/or the other structures from damage. For example, in the case of an undersea optical cable the cable may cross over an undersea oil or gas pipeline. To avoid damage to the cable and/or the pipeline, the cable is often encompassed within a separation duct. The separation duct establishes a separation distance between the cable and the pipeline and may be formed of a material that will not damage the pipeline in the event of contact between the pipeline and the separation duct. One example of such a separation duct is described in U.S. Patent Application Publication No. US2007/0051419, the teachings of which are hereby incorporated herein by reference.
One challenge associated with known separation duct configurations is that there has been a need match the internal dimensions of the separation duct with the external dimensions of the elongate member to be received thereby. If the separation duct is too large compared to the cable, the separation duct may not properly grip the cable and may slip along the length thereof to an undesirable position. If the separation duct is too small, it may not fit around the cable. These problems are exacerbated when, for example, an elongate member and separation duct are deployed via a ship at sea and the ship has been mistakenly loaded with separation duct of an incorrect size. In such a case, the ship may be required to return to port to obtain a correct size of separation duct and then return to the location where the elongate member is to be deployed. This can result in significant delays and cost increases associated with deployment of the elongate member.